Do you think Wikipedia in 5 years will be as good or better than it is
now? I?ve spent a bit of time using Wikipedia as a reference, and I
even saw an article comparing Wikipedia to the Encyclopedia Britannica
in terms of article quality. But do you think that Wikipedia can
sustain itself while sticking to the ?anyone can contribute? model for
the long-run?

In less than 5 years, Wikipedia will be swallowed by Google.

(Oops, sorry if I've give away any sensitive information.)

Maybe, it would be easy for Google to offer so much money that the
principles of the persons in control of the site caved in.
I would like to think that Google recognizes that it shouldn't
monopolize internet and understands that the charm of Wikipedia is the
unique way it works  - maybe realizing that it could be "killed"
almost overnight by the people who post articles.  At the first sign
of a takeover, they could gang up and dismantle the site  - or wait
and do that after the takeover.  Meanwhile, a new "Vikipedia" could be
established and restocked.

I hope someone in Mountain View is reading.

But that wasn't the question.  Despite the questions about Wikipedia's
system, it works extremely well.  Maybe the enthusiasm will die down,
but I see no reason why it should not maintain its quality  - if it
continues to exist.

Just one man's opinion.

I think Wikipedia is likely to thrive if it follows the path being
forged by The Citizendium Project:

http://citizendium.org/

Wikipedia uses the GNU Free Documentation License. Check

http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License

and also

http://www.gnu.org/licenses/fdl.html

for details. What this means is that basically anyone can copy everything in it
and offer it under the same terms (and it has copyleft, which means they cannot 
use other terms). If Google or anyone else buys it and runs it in any way 
contrary to the open spirit with which it is run today, anyone can just copy
everything in it and start a new site if they don't like the new rules.

Conversely though Google does not have to buy wikipedia (although they probably 
can do it using just their petty cash). They can also copy everything and start 
their own competitor site.

In both cases though the final judge will be the users. And the users typically 
favor openess and transparency of operation. The best system will almost 
certainly have these features, unless it can be restricted. And the GNU FDL 
with its copyleft features mean that this cannot be done, either in wikipedia, 
or any possible derivative.

In short I wouldn't worry. The situation is similar to that of Linux, which 
has been growing for 16 years and remains free, despite all attempts to the 
contrary, thanks to its GNU licence.